1. Technical Field
The present invention relates to a circuit board, particularly a circuit board comprising electrode structure with good drop resistance and manufacturing method thereof.
2. Background Art
Circuit boards comprising BGA (Ball Grid Array) are used in various fields. BGA electrode structure comprising a nickel (Ni) layer between a conductor layer (electrode pad of circuits) and solder pad (solder ball) is disclosed in Japanese published unexamined application No. H10-154876 publication. Furthermore, an electrode structure comprising a nickel alloy layer such as Ni—Sn between a nickel layer and a solder bump is disclosed in Japanese published unexamined application No. 2006-114706 publication. The entire content of each of H10-154876 and 2006-114706 is incorporated herein by reference.
Circuit substrates comprising BGA are used by incorporating them in various devices, and some of them are used for portable electronic devices, for example, cell phones. Circuit substrates used for portable devices are required to be good in drop resistance property. This is because portable devices themselves are often dropped while in use.